Japanese unexamined patent application no. JP-A-2003-295562 describes a related art image forming apparatus such as a color printer. The related art image forming apparatus includes a plurality of process cartridges each having a photosensitive drum and a plurality of developer supply units each containing developer to be supplied to the process cartridge. A door provided to be openable and closable at the front side of the apparatus is opened, so that the process cartridge and the developer supply unit can be attached to and detached from a printer main body by so-called front access.